mc908jl16 Freescale Semiconductor, Inc, mc908jl16 Datasheet - Page 199

• Manufacturer Part Number: mc908jl16
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

start of boundary address (the page start address: $XX00, $XX40, $XX80, or $00C0) and DATASIZE
must be the same size when accessing the same page.
In some applications, the user may want to repeatedly store and read a set of data from an area of
non-volatile memory. This can be easily implemented when EEPROM memory is used because the byte
erase is allowed in EEPROM. On the other hand in FLASH memory, a minimum erase size is a page (64
bytes), so unused locations in a page will be wasted when it is used for data storage.
The EE_WRITE routine is designed to emulate EEPROM using FLASH. This allows a FLASH page to
implement data storage more efficiently. Each call of the EE_WRITE routine will automatically transfer the
data in the data array (in RAM) to the next available blank locations in a page. Once the page is filled up
with data, the EE_WRITE routine automatically erases the page and programs updated data in the same
page. In a FLASH page, data is programmed to FLASH with in a block that consists of the data array and
one boundary byte. The boundary byte contains the remaining number of bytes which can be
programmed in the page (see
When using this routine to store a 3-byte data array, the FLASH page can be programmed 16 times before
the an erase is required. In effect, the write/erase endurance is increased by 16 times. When a 15-byte
data array is used, the write/erase endurance is increased by 4 times. Due to the FLASH page size
limitation, the data array is limited from 2 bytes to 15 bytes.
The coding example below uses the $EF00–$EE3F page for data storage. The data array size is 15 bytes,
and the bus speed is 4.9152 MHz. The coding assumes the data block is already loaded in RAM, with the
address pointer, FILE_PTR, pointing to the first byte of the data block.
Freescale Semiconductor
ONE PAGE = 64 BYTES
PAGE START
PAGE END
Figure 16-16. EE_WRITE FLASH Memory Usage
Figure
MC68HC908JL16 Data Sheet, Rev. 1.1
16-16).
F
DATA ARRAY
DATA ARRAY
DATA ARRAY
BOUNDARY
BOUNDARY
BOUNDARY
L
A
S
H
$XX00, $XX40, $XX80, OR $XXC0
Monitor Module (MON)
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